Key Takeaway
The four main types of pressure gauges are Bourdon tube, diaphragm, capsule, and bellows gauges.
Bourdon tube gauges are the most common and are used for medium to high-pressure measurements.
Diaphragm gauges are ideal for low-pressure and corrosive media, using a flexible membrane.
Capsule gauges are used for very low-pressure measurements in gas systems.
Bellows gauges use accordion-like elements to measure differential or low pressure.
Each type is chosen based on pressure range, fluid compatibility, and application environment. These gauges convert mechanical movement into readable dial indicators and are essential in numerous industrial and laboratory applications.
Bourdon Tube Gauges
Bourdon tube gauges are the most widely used pressure measuring instruments in industrial environments. They consist of a curved, C-shaped metal tube that straightens out when pressurized.
This mechanical movement is transferred through a linkage system to a pointer needle, which moves across a calibrated dial. It’s a simple yet elegant mechanism.
They’re used in steam systems, compressors, hydraulic presses, and more. Why? Because they’re affordable, reliable, and don’t require external power.
They come in different pressure ranges — from vacuum to 1000+ bar — and in different materials (brass, stainless steel, etc.) depending on the application. They’re rugged, but not immune to fatigue. Mechanical wear, vibration, and overpressure can cause needle sticking or permanent deflection. Periodic inspection is necessary.
Diaphragm Gauges
Diaphragm gauges use a thin, flexible metal disc as the sensing element. When pressure is applied, the diaphragm flexes. This motion is then translated mechanically (via linkages) or electronically (via strain gauges) into a readable value.
They are ideal for:
Low-pressure measurements
Corrosive fluids
Slurries or viscous media
Because the process fluid doesn’t directly contact the mechanical parts, diaphragm gauges last longer in harsh environments. You’ll often find them in water treatment, pharma, food, and chemical industries.
Diaphragm gauges may be dry or liquid-filled and are available with flanged or threaded connections. They also support sanitary designs for hygienic applications.
Capsule and Bellows Gauges
Both capsule and bellows gauges are used for low-pressure measurements — typically below 600 mbar.
Capsule gauges have two diaphragms welded at the edges. Pressure inflates the capsule like a balloon.
Bellows gauges have accordion-like metal structures that expand or compress with pressure.
Applications include:
Gas pressure measurement
HVAC systems
Clean rooms
Leak detection
They’re sensitive, accurate, and excellent for differential readings. Use them when Bourdon tubes aren’t sensitive enough for low-pressure tasks.
Digital and Electronic Gauges
Digital pressure gauges offer clear numeric displays, eliminating parallax and misreading errors. Powered by strain gauge or piezoresistive sensors, they convert pressure into electrical signals and display accurate, stable readings.
Advantages:
High accuracy (±0.1% or better)
Backlit displays for dark zones
Peak hold, min/max memory
Alarm setpoints
Data logging or transmission (4–20 mA, RS485, etc.)
They’re perfect for regulated industries, labs, or remote monitoring setups. While costlier upfront, digital gauges offer long-term value through precision, functionality, and integration with control systems.
When to Use Each Type
There are several types of pressure gauges, each suited for different applications:
Bourdon Tube Gauges: Ideal for medium to high-pressure systems. Widely used in industrial applications.
Diaphragm Gauges: Used for low pressure, corrosive fluids, or hygienic applications. Common in food, pharma, and chemical industries.
Capsule Gauges: Best for very low-pressure gas measurement.
Digital Gauges: Preferred when high accuracy, data logging, or integration with SCADA/PLC systems is required.
Differential Gauges: Used to measure the difference between two pressures, such as across a filter or orifice.
Selection depends on factors like:
Pressure range
Fluid type (liquid/gas, corrosive or clean)
Required precision
Environmental conditions (vibration, temperature, IP rating)
Regulatory or hygienic needs
Always select based on your operating range, accuracy requirement, and system type. For example, a Bourdon gauge wouldn’t suit a medical ventilator — but a digital or capsule gauge might. Using the wrong type can lead to frequent recalibration, errors, or even safety hazards.
Conclusion
A pressure gauge isn’t just a device—it’s a safety component. It helps prevent catastrophic failures caused by overpressure or system leaks. By offering real-time feedback, it gives operators the chance to act before something goes wrong. Whether in a steam boiler, hydraulic system, or gas pipeline, pressure gauges are the first alert mechanism. They’re also crucial during startup, maintenance, and emergency shutdowns. When properly installed, maintained, and calibrated, they offer a reliable way to keep operations within safe limits. Safety standards in many industries require pressure monitoring, and the humble gauge fulfills this role brilliantly. It’s cost-effective, easy to install, and always on guard—making it a must-have for system protection.